Semiconductor device manufacturing method and semiconductor device

ABSTRACT

A technique is provided which makes it possible to achieve both of a reduction in contact resistance in a memory device and a reduction in contact resistance in a logic device even when oxidation is performed during formation of dielectric films of capacitors. Conductive barrier layers ( 82 ) are provided in the top ends of contact plugs ( 83   b ) electrically connected to ones of source/drain regions ( 59 ). Lower electrodes ( 70 ) of capacitors ( 73 ) are formed in contact with the conductive barrier layers ( 82 ) of the contact plugs ( 83   b ) and then dielectric films ( 71 ) and upper electrodes ( 72 ) of the capacitors ( 73 ) are sequentially formed. In the logic region, contact plugs ( 25 ) are formed in an upper layer so that they are in contact respectively with contact plugs ( 33 ) electrically connected to source/drain regions ( 9 ).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a merged memory-logic semiconductordevice having a memory device and a logic device formed on asemiconductor substrate, and to a method for manufacturing thesemiconductor device.

2. Description of the Background Art

The recent miniaturization of merged memory-logic semiconductor devicesis leading to reduction of memory cell areas. Accordingly, in order toensure certain capacitor capacitance even with reduced memory cellareas, MIM (Metal-Insulator-Metal) capacitors are now often adopted asmemory cell capacitors.

When MIM capacitors are adopted as memory cell capacitors, the processof forming the dielectric film may oxidize contact plugs connected tothe lower electrodes and neighboring contact plugs to increase thecontact resistance. In order to solve this problem, Japanese PatentApplication Laid-Open No. 2001-267516 discloses a technique forpreventing the increase in contact resistance by providing anoxidation-preventing barrier layer on top ends of contact plugs. Also,Japanese Patent Application Laid-Open Nos. 2001-284541 and 10-150161(1998) disclose techniques about semiconductor devices with capacitors.

However, with merged memory-logic semiconductor devices, it is difficultto achieve both of a reduction in contact resistance in the memorydevice and a reduction in contact resistance in the logic device.

SUMMARY OF THE INVENTION

An object of the invention is to provide a technique which makes itpossible to achieve both of a reduction in contact resistance in amemory device and a reduction in contact resistance in a logic deviceeven when oxidation is performed during formation of dielectric films ofMIM capacitors.

A semiconductor device manufacturing method of the invention includessteps (a) to (d). The step (a) is to form a first insulating film on asemiconductor substrate having a memory region where a memory device isto be formed and a logic region where a logic device is to be formed.The step (b) is to form, in the first insulating film, a first contactplug electrically connected to the semiconductor substrate in the memoryregion and having its top surface exposed from the first insulatingfilm, and a second contact plug electrically connected to thesemiconductor substrate in the logic region and having its top surfaceexposed from the first insulating film. The first contact plug formed inthe step (b) has a first conductive film and a first conductive barrierlayer formed on a top end of the first contact plug. The step (c) is toform an MIM capacitor in contact with the first conductive barrier layerand forms a second insulating film, covering the MIM capacitor, on a topsurface of the structure obtained by the step (b). After the step (c),the step (d) is to form, in the second insulating film, a third contactplug in contact with the second contact plug. The MIM capacitor formedin the step (c) has a lower electrode in contact with the firstconductive barrier layer, an upper electrode, and a dielectric filminterposed therebetween.

The first contact plug connected to the MIM capacitor has the firstconductive barrier layer in its top end, so that the first conductivefilm of the first contact plug is not oxidized during formation of thedielectric film of the MIM capacitor. This lowers the contact resistancebetween the MIM capacitor and the semiconductor substrate in the memoryregion. Furthermore, adopting the stacked structure in the logic regionreduces inferior contacts due to increased aspect ratios of contactplugs. It is thus possible to achieve both of a reduction in contactresistance in the memory device and a reduction in contact resistance inthe logic device even when formation of the dielectric film of the MIMcapacitor involves oxidation process.

A first semiconductor device of the invention includes a semiconductorsubstrate, first and second insulating films, first to third contactplugs, and an MIM capacitor. The semiconductor substrate has a memoryregion where a memory device is formed and a logic region where a logicdevice is formed. The first insulating film is provided on thesemiconductor substrate. The first contact plug is provided in the firstinsulating film with its top surface exposed from the first insulatingfilm, and is electrically connected to the semiconductor substrate inthe memory region. The second contact plug is provided in the firstinsulating film with its top surface exposed from the first insulatingfilm, and is electrically connected to the semiconductor substrate inthe logic region. The MIM capacitor has a lower electrode, an upperelectrode, and a dielectric film interposed therebetween and the lowerelectrode is in contact with the top surface of the first contact plug.The second insulating film is provided on the first insulating film andcovers the MIM capacitor. The third contact plug is provided in thesecond insulating film and is in contact with the second contact plug.The first contact plug has a first conductive barrier layer in its topportion and a first conductive film in the remaining portion. The secondcontact plug has a second conductive barrier layer in its top portionand has, in the remaining portion, a second conductive film having ahigher conductivity than the second conductive barrier layer. The thirdcontact plug extends into the first insulating film and is in contactwith the second conductive barrier layer and a side surface of thesecond conductive film.

Even though the second contact plug in the logic region has the secondconductive barrier layer, the third contact plug in the upper layer isin contact not only with the second conductive barrier layer of thelower-layer second contact plug but also with the second conductive filmhaving a higher conductivity. This lowers the contact resistance betweenthe third contact plug and the semiconductor substrate in the logicregion. Furthermore, the first contact plug in contact with the MIMcapacitor has the first conductive barrier layer in its top, whichprevents oxidation of the first conductive film of the first contactplug during formation of the dielectric film of the MIM capacitor. It isthus possible to achieve both of a reduction in contact resistance inthe memory device and a reduction in contact resistance in the logicdevice even when the formation of the dielectric film of the MIMcapacitor involves oxidation process.

A second semiconductor device of the invention includes a semiconductorsubstrate, first and second insulating films, first to fifth contactplugs, and an MIM capacitor. The semiconductor substrate has a memoryregion where a memory device is formed and a logic region where a logicdevice is formed. The first insulating film is provided on thesemiconductor substrate. The first and second contact plugs are providedin the first insulating film with their respective top surfaces exposedfrom the first insulating film, and are electrically connected to thesemiconductor substrate in the memory region. The third contact plug isprovided in the first insulating film with its top surface exposed fromthe first insulating film, and is electrically connected to thesemiconductor substrate in the logic region. The MIM capacitor has alower electrode, an upper electrode, and a dielectric film interposedtherebetween, and the lower electrode is in contact with the top surfaceof the first contact plug. The second insulating film is provided on thefirst insulating film and covers the MIM capacitor. The fourth contactplug is provided in the second insulating film and is in contact withthe second contact plug. The fifth contact plug is provided in thesecond insulating film and is in contact with the third contact plug.The first contact plug has a first conductive barrier layer in its topportion and a first conductive film in the remaining portion. The secondcontact plug has a second conductive barrier layer in its top portionand has, in the remaining portion, a second conductive film having ahigher conductivity than the second conductive barrier layer. The fourthcontact plug extends into the first insulating film and is in contactwith the second conductive barrier layer and a side surface of thesecond conductive film.

Even though the second contact plug in the memory region has the secondconductive barrier layer, the fourth contact plug in the upper layer isin contact not only with the second conductive barrier layer of thelower-layer second contact plug but also with the second conductive filmhaving a higher conductivity. This lowers the contact resistance betweenthe fourth contact plug and the semiconductor substrate in the memoryregion. Furthermore, the first contact plug in contact with the MIMcapacitor has a first conductive barrier layer in its top, whichprevents oxidation of the first conductive film of the first contactplug during formation of the dielectric film of the MIM capacitor. It isthus possible to achieve both of a reduction in contact resistance inthe memory device and a reduction in contact resistance in the logicdevice even when the formation of the dielectric film of the MIMcapacitor involves oxidation process.

These and other objects, features, aspects and advantages of the presentinvention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 16 are cross-sectional views showing a sequence of processsteps for manufacturing a semiconductor device according to a firstpreferred embodiment of the invention;

FIGS. 17 to 21 are cross-sectional views showing the structures ofsemiconductor devices that can be manufactured according to the firstpreferred embodiment of the invention;

FIGS. 22 to 30 are cross-sectional views showing a sequence of processsteps for manufacturing a semiconductor device according to a secondpreferred embodiment of the invention;

FIGS. 31 to 35 are cross-sectional views showing the structures ofsemiconductor devices that can be manufactured according to the secondpreferred embodiment of the invention;

FIGS. 36 to 42 are cross-sectional views showing a sequence of processsteps for manufacturing a semiconductor device according to a thirdpreferred embodiment of the invention;

FIGS. 43 to 47 are cross-sectional views showing the structures ofsemiconductor devices that can be manufactured according to the thirdpreferred embodiment of the invention;

FIGS. 48 to 50 are cross-sectional views showing a sequence of processsteps for manufacturing a semiconductor device according to a fourthpreferred embodiment of the invention;

FIG. 51 is a cross-sectional view showing the structure of asemiconductor device according to a fifth preferred embodiment of theinvention;

FIGS. 52 to 55 are cross-sectional views showing a sequence of processsteps for manufacturing the semiconductor device of the fifth preferredembodiment of the invention;

FIG. 56 is a cross-sectional view showing the structure of amodification of the semiconductor device of the fifth preferredembodiment of the invention;

FIGS. 57 and 58 are cross-sectional views showing a sequence of processsteps for manufacturing the modification of the semiconductor device ofthe fifth preferred embodiment of the invention;

FIGS. 59 to 63 are cross-sectional views showing the structures ofmodifications of the semiconductor device of the fifth preferredembodiment of the invention;

FIG. 64 is a cross-sectional view showing the structure of asemiconductor device according to a sixth preferred embodiment of theinvention;

FIGS. 65 to 67 are cross-sectional views showing a sequence of processsteps for manufacturing the semiconductor device of the sixth preferredembodiment of the invention;

FIG. 68 is a cross-sectional view showing the structure of amodification of the semiconductor device of the sixth preferredembodiment of the invention;

FIGS. 69 and 70 are cross-sectional views showing a sequence of processsteps for manufacturing the modification of the semiconductor device ofthe sixth preferred embodiment of the invention; and

FIGS. 71 to 75 are cross-sectional views showing the structures ofmodifications of the semiconductor device of the sixth preferredembodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Preferred Embodiment

FIGS. 1 to 16 are cross-sectional views showing a sequence of processsteps for manufacturing a semiconductor device according to a firstpreferred embodiment of the present invention. The semiconductor deviceof the first preferred embodiment is a merged memory-logic semiconductordevice; for example, it has, as a memory device, a DRAM with CUB(Capacitor Under Bit Line) structured memory cells, and also hassalicide CMOS transistors as a logic device. The capacitors of the DRAMmemory cells are concave-type MIM capacitors, for example. Thesemiconductor device manufacturing method of the first preferredembodiment will now be described referring to FIGS. 1 to 16.

First, as shown in FIG. 1, element isolation insulating films 2 areformed in the upper surface of a semiconductor substrate 1, e.g. ann-type silicon substrate, by a known LOCOS isolation technique or trenchisolation technique. Then a p-type well region 53 is formed in the uppersurface of the semiconductor substrate 1 in the region for formation ofthe memory device (hereinafter referred to as “a memory region”) and ap-type well region 3 is formed in the upper surface of the semiconductorsubstrate 1 in the region for formation of the logic device (hereinafterreferred to as “a logic region).

Next, in the memory region, a plurality of n-type source/drain regions59 are formed at given distances from each other in the upper surface ofthe well region 53, and gate structures 61 are formed on the uppersurface of the well region 53 between the source/drain regions 59. Inthe logic region, a plurality of n-type source/drain regions 9 areformed at a given distance in the upper surface of the well region 3 anda gate structure 11 is formed on the upper surface of the well region 3between the source/drain regions 9.

Each gate structure 61 in the memory region has: a gate insulating film55, e.g. a silicon oxide film; a gate electrode 56, e.g. apolycrystalline silicon film; and sidewalls 60, e.g. silicon nitridefilms. After the formation of the gate structures 61, the gateinsulating films 55 lie on the top surface of the well region 53 betweenthe source/drain regions 59, with the gate electrodes 56 lying on thegate insulating films 55. The sidewalls 60 reside on the sides of thegate insulating films 55 and gate electrodes 56.

The gate structure 11 in the logic region has: a gate insulating film 5,e.g. a silicon oxide film; a gate electrode 6, e.g. a polycrystallinesilicon film; and sidewalls 10, e.g. silicon nitride films. After theformation of the gate structure 11, the gate insulating film lies on thetop surface of the well region 3 between the source/drain regions 9,with the gate electrode 6 lying on the gate insulating film 5. Thesidewalls 10 reside on the sides of the gate insulating film 5 and gateelectrode 6.

Next, the top surfaces of the gate electrodes 6 and 56 and the topsurfaces of the source/drain regions 9 and 59 are silicidized to formsilicide films 12 on the top surfaces of the gate electrodes 6 and 56and silicide films 12 on the top surfaces of the source/drain regions 9and 59. The silicide films 12 may be cobalt silicide films, for example.

Next, as shown in FIG. 2, an insulating film 14 is formed on thesemiconductor substrate 1 to cover the gate structures 11 and 61. Theinsulating film 14, e.g. a BPTEOS film, functions as an interlayerinsulating film.

Next, resist (not shown) having a given opening pattern is formed on theinsulating film 14 by photolithography and then the insulating film 14is partially etched and removed away using the resist. This etchingadopts an anisotropic dry-etching using a mixed gas of C₄F₆, O₂, and Ar.Then the resist used as a mask is removed.

Thus, as shown in FIG. 3, in the memory region, contact holes 65 areformed in the insulating film 14 to reach the silicide films 12 on thesemiconductor substrate 1; in the logic region, contact holes 15 areformed in the insulating film 14 to reach the silicide films 12 on thesemiconductor substrate 1.

Next, a refractory metal film of, e.g. tungsten, is formed all over thesurface to fill the contact holes 15 and 65. Then, the refractory metalfilm on the top surface of the insulating film 14 is removed, e.g. byCMP. Thus, as shown in FIG. 4, in the insulating film 14, conductivefilms 16 of refractory metal fill the contact holes 15 and conductivefilms 66 of refractory metal fill the contact holes 65.

Next, as shown in FIG. 5, a resist 30, adapted for excimer exposure, isformed all over the surface, and a photolithography process using anexcimer laser as the light source is applied to the resist 30 to form anopening pattern that exposes the top surfaces of conductive films 66that will be electrically connected to capacitors formed later. Then, asshown in FIG. 6, using the resist 30 as a mask, the exposed portions areetched to selectively remove upper parts of the conductive films 66 thatare to be connected with capacitors. This process forms recesses 81 inthe insulating film 14 in the memory region. This etching process adoptsan anisotropic dry-etching using SF₆ as the etching gas.

Next, as shown in FIG. 7, the resist 30 used as a mask is removed. Then,a barrier layer material, formed of, e.g. titanium nitride (TiN),tantalum nitride (TaN), or titanium silicide nitride (TiSiN), is formedall over the surface to fill the recesses 81, and the barrier layermaterial is removed above the recesses 81, e.g. by CMP. Thus, as shownin FIG. 8, conductive barrier layers 82 of, e.g. titanium nitride,tantalum nitride, or titanium silicide nitride, fill the recesses 81 inthe insulating film 14.

The process steps above thus form a contact plug 83 a and contact plugs83 b in the insulating film 14 in the memory region; the contact plug 83a is formed of the conductive film 66, and the contact plugs 83 b areeach formed of the conductive barrier layer 82 in the upper part and theconductive film 66 in the remaining part. In the logic region, contactplugs 33 made of the conductive film 16 are thus formed in theinsulating film 14. As can be clearly seen from the materials used, theconductive barrier layers 82 exhibit lower conductivity than theconductive films 16 and 66.

The contact plugs 33 have their top surfaces exposed from the insulatingfilm 14 and are electrically connected through the silicide films 12 tothe source/drain regions 9 in the upper surface of the semiconductorsubstrate 1.

The contact plug 83 a has its top surface exposed from the insulatingfilm 14 and is electrically connected through the silicide film 12 toone of the adjacent source/drain regions 59 that is to be electricallyconnected to a bit line formed later.

The contact plugs 83 b have their top surfaces, i.e. the top surfaces ofconductive barrier layers 82, exposed from the insulating film 14, andare electrically connected through silicide films 12 to ones of theadjacent source/drain regions 59 that are to be electrically connectedto capacitors formed later.

Next, as shown in FIG. 9, a stopper film 17, e.g. a silicon nitridefilm, is formed on the insulating film 14 and contact plugs 33, 83 a,and 83 b. Then an interlayer insulating film 18 is formed on the stopperfilm 17. BPTEOS film is adopted as the interlayer insulating film 18,for example.

Next, a resist (not shown) having a given opening pattern is formed onthe interlayer insulating film 18. Then, using the resist as a mask, theinterlayer insulating film 18 is etched away using the stopper film 17as an etching stopper. This etching adopts an anisotropic dry-etchingprocess using a mixed gas of C₄F₆, O₂, and Ar.

Then, using again as a mask the resist used to etch the interlayerinsulating film 18, the exposed parts of the stopper film 17 are etchedand removed away and then the resist is removed. This etching adopts ananisotropic dry-etching process using CHF₃ as the etching gas. Thus, asshown in FIG. 10, openings 69 are formed through the interlayerinsulating film 18 and stopper film 17, exposing the contact plugs 83 bthat are to be connected with capacitors.

Next, DRAM memory cell capacitors are formed in the openings 69; thecapacitors are formed in contact with the conductive barrier layers 82of the contact plugs 83 b. More specifically, a lower electrodematerial, e.g. ruthenium (Ru), titanium nitride (TiN), or platinum (Pt),is formed all over the surface. Then, with resist (not shown) fillingthe openings 69, the lower electrode material on the top surface of theinterlayer insulating film 18 is removed by anisotropic dry-etching, andthen the resist is removed. Thus, as shown in FIG. 11, capacitor lowerelectrodes 70, of ruthenium, titanium nitride, or platinum, are formedin the openings 69. While the description said that the lower electrodematerial on top of the interlayer insulating film 18 is removed byanisotropic dry-etching, the electrode material may be removed by CMP.

Next, a dielectric film material formed of, e.g. tantalum oxide (Ta₂O₅),aluminum oxide (Al₂O₃), or barium strontium titanate (BST), and an upperelectrode material of, e.g. ruthenium, titanium nitride, or platinum,are stacked in this order all over the surface, which are patternedusing resist. This forms, as shown in FIG. 12, capacitor upperelectrodes 72 of, e.g. ruthenium, titanium nitride, or platinum, andcapacitor dielectric films 71 of tantalum oxide, aluminum oxide, orbarium strontium titanate between the lower electrodes 71 and upperelectrodes 72; capacitors 73 are thus completed in the openings 69.

Now, the formation of dielectric films 71 of MIM capacitors 73 uses anMOCVD (Metal Organic CVD) process that uses organic metal material gas.This MOCVD process includes an oxygen adding process involving UV-O₃oxidation or plasma oxidation during the deposition of the dielectricfilm material, and also includes a lamp anneal process forcrystallization in an oxygen atmosphere after the deposition. During theprocess, produced oxidation species pass through the lower electrodes 70to reach the contact plugs 83 b; therefore, in the absence of theconductive barrier layers 82, the conductive films 66 of contact plugs83 b will be oxidized. However, in the first preferred embodiment, theconductive barrier layers 82 in the top ends of the contact plugs 83 bserve as oxidation preventing films, preventing oxidation of theconductive films 66 of contact plugs 83 b during the formation of thedielectric films 71 of capacitors 73.

Next, as shown in FIG. 13, an interlayer insulating film 23, e.g. a TEOSfilm, is formed on the upper electrodes 72 of capacitors 73 and theinterlayer insulating film 18 and is then planarized by CMP. Thus, aninsulating film 31, which includes the stopper film 17 and interlayerinsulating films 18 and 23, is formed on the insulating film 14 andcontact plugs 33 and 83 a and covers the capacitors 73.

Next, as shown in FIG. 14, a resist 38 is formed on the insulating film31, with opening patterns 39 a positioned in correspondence with thecontact plugs 33 and an opening pattern 39 b positioned incorrespondence with the contact plug 83 a. Then, using the resist 38 asa mask, the interlayer insulating films 18 and 23 are partially etchedand removed away using the stopper film 17 as an etching stopper. Thisetching adopts an anisotropic dry-etching process using a mixed gas ofC₄F₆, O₂, and Ar. Then, using the resist 38 as a mask again, the exposedparts of the stopper film 17 are etched away. This etching adopts ananisotropic dry-etching process using CHF₃ as the etching gas.

Contact holes 24 are thus formed in the insulating film 31 torespectively reach the contact plugs 33 and a contact hole 74 is formedto reach the contact plug 83 a.

Next, the resist 38 is removed, and a refractory metal film of, e.g.tungsten, is formed all over the surface to fill the contact holes 24and 74. Then, the refractory metal film on the top surface of theinsulating film 31 is removed, e.g. by CMP. Thus, as shown in FIG. 15,contact plugs 25 of refractory metal which fill contact holes 24 areformed in the insulating film 31 in the logic region, with the contactplugs 33 and contact plugs 25 respectively in contact with each other.Also, a contact plug 75 of refractory metal which fills the contact hole74 is formed in the insulating film 31 in the memory region, with thecontact plug 83 a and contact plug 75 in contact with each other.

Next, as shown in FIG. 16, interconnections 26, in contact with thecontact plugs 25, are formed on the insulating film 31, and a DRAMmemory cell bit line 76 in contact with the contact plug 75 is formed onthe insulating film 31. The interconnections 26 and bit line 76 may beformed of aluminum interconnections, for example.

Through the process steps shown above, a memory device havingconcave-type MIM capacitors is formed in the memory region and a logicdevice with stacked structure is formed in the logic region.

As described so far, according to the semiconductor device manufacturingmethod of the first preferred embodiment, the oxidation-preventingconductive barrier layers 82 reside in the top ends of the contact plugs83 b that are connected with the capacitors 73, which prevent oxidationof the conductive films 66 of the contact plugs 83 b during formation ofthe dielectric films 71 of capacitors 73. This reduces the contactresistance between the capacitors 73 and source/drain regions 59.Furthermore, adopting the stacked structure in the logic region avoidsinferior contacts due to increased aspect ratios of contact plugs. It isthus possible to achieve both of a reduction in contact resistance inthe memory device and a reduction in contact resistance in the logicdevice, even when oxidation process is performed during formation of thedielectric films 71 of capacitors 73 as described in the first preferredembodiment.

While the first preferred embodiment has shown a method formanufacturing a semiconductor device that has concave-type MIMcapacitors as DRAM memory cell capacitors 73, the present invention canbe applied also to methods for manufacturing semiconductor devices inwhich capacitors 73 are MIM capacitors of other structures. For example,the present invention can be applied also to methods for manufacturingsemiconductor devices having supported cylinder-type MIM capacitors asshown in FIG. 17, pillar-type MIM capacitors as shown in FIG. 18, andthick-film stacked-type MIM capacitors as shown in FIG. 19.

When supported cylinder-type MIM capacitors are adopted as capacitors73, the accumulated capacitance can be increased as compared with thatof the semiconductor device of the first preferred embodiment. Whenpillar-type MIM capacitors are adopted or thick-film stacked-type MIMcapacitors are adopted, good film formation coverage is obtained duringformation of the upper electrodes 72, which lowers the leakage currentof capacitors 73 as compared with the semiconductor device of the firstpreferred embodiment.

When pillar-type MIM capacitors or thick-film stacked-type MIMcapacitors are adopted, the aspect ratios of the contact plugs 25, 75can be smaller. Therefore, as shown in FIGS. 20 and 21, the contactplugs 25 and interconnections 26, or the contact plug 75 and bit line 76may be integrally formed using dual damascene process.

When thick-film stacked-type MIM capacitors are adopted, the interlayerinsulating film 18 in the insulating film 31 is removed during themanufacturing process. Therefore FIGS. 19 and 21 do not show it.

While the first preferred embodiment uses a mixed gas of C₄F₆, O₂, andAr to etch the insulating film 14 and interlayer insulating films 18 and23, a mixed gas of C₅F₈ or C₄F₆, O₂, and Ar may be used.

Second Preferred Embodiment

The first preferred embodiment provides the conductive barrier layers 82in the top ends of the contact plugs 83 b that are connected tocapacitors 73. However, during the formation of the dielectric films 71of capacitors 73, not only the contact plugs 83 b but also theneighboring contact plug 83 a in the memory region may be oxidized.

Accordingly, a second preferred embodiment describes a manufacturingmethod in which conductive barrier layer 82 is formed also in the topend of the contact plug 83 a that is electrically connected to the DRAMmemory cell bit line 76.

FIGS. 22 to 30 are cross-sectional views showing a sequence of processsteps for manufacturing a semiconductor device according to the secondpreferred embodiment of the invention. First, the structure shown inFIG. 4 is obtained according to the manufacturing process of the firstpreferred embodiment. Then, as shown in FIG. 22, resist 35 adapted fori-line exposure is formed all over the surface, and an opening patternthat opens the memory region is formed in the resist 35 byphotolithography using i-line as the light source. Then, as shown inFIG. 23, the exposed part is etched using the resist 35 as a mask toselectively remove the top ends of the conductive films 66 that are tobe electrically connected to capacitors 73 and the top end of theconductive film 66 that is to be electrically connected to the bit line76. Recesses 81 are thus formed in the insulating film 14 in the memoryregion. This etching adopts an anisotropic dry-etching process using SF₆as the etching gas.

In the second preferred embodiment, unlike in the first preferredembodiment, an opening pattern that opens the entire memory region isformed in the resist 35, since it is not necessary to resist-mask theconductive film 66 electrically connected to the bit line 76. Thereforethe second preferred embodiment can adopt i-line-exposure-adapted resist35 that is less expensive than the excimer-exposure-adapted resist 30used in the first preferred embodiment. It is therefore possible to useless expensive exposure apparatus to form the opening pattern in theresist 35 than in the first preferred embodiment.

Next, as shown in FIG. 24, the resist 35 used as a mask is removed.Then, a barrier layer material of, e.g. titanium nitride, tantalumnitride, or titanium silicide nitride, is formed all over the surface tofill the recesses 81, and the barrier layer material above the recesses81 is removed, e.g. by CMP. Thus, as shown in FIG. 25, conductivebarrier layers 82 filling the recesses 81 are formed in the insulatingfilm 14.

These process steps form a contact plug 83 a and contact plugs 83 b inthe insulating film 14 in the memory region; the contact plug 83 a iselectrically connected to one of adjacent source/drain regions 59 andhas the conductive barrier layer 82 in the top portion and theconductive film 66 in the remaining portion, and the contact plugs 83 bare electrically connected to others of adjacent source/drain regions 59and each have the conductive barrier layer 82 in the top portion and theconductive film 66 in the remaining portion. In the logic region,contact plugs 33 of conductive film 16 are formed in the insulating film14.

Next, as shown in FIG. 26, stopper film 17 and interlayer insulatingfilm 18 are deposited in this order on the insulating film 14 andcontact plugs 33, 83 a and 83 b. Then, as shown in FIG. 27, as in thefirst preferred embodiment, openings 69, capacitors 73, and interlayerinsulating film 23 are sequentially formed. The capacitors 73 shown inFIG. 27 are concave-type MIM capacitors.

Next, as shown in FIG. 28, resist 38 having opening patterns 39 a and 39b is formed on the insulating film 31. The interlayer insulating films18 and 23 and stopper film 17 are etched and removed away using theresist 38 as a mask. This process forms contact holes 24 respectivelyreaching the contact plugs 33 and a contact hole 74 reaching theconductive barrier layer 82 of the contact plug 83 a in the insulatingfilm 31.

Next, after removal of resist 38, as shown in FIG. 29, contact plugs 25filling the contact holes 24 and contact plug 75 filling the contacthole 74 are formed. Thus the contact plugs 33 and contact plugs 25 arein contact respectively with each other and the conductive barrier layer82 of the contact plug 83 a and the contact plug 75 are in contact witheach other.

Next, as shown in FIG. 30, interconnections 26 and bit line 76 areformed on the insulating film 31.

Thus, a memory device is formed in the memory region and a logic deviceis formed in the logic region.

As described above, according to the semiconductor device manufacturingmethod of the second preferred embodiment, the oxidation-preventingconductive barrier layers 82 are formed not only in the top ends of thecontact plugs 83 b connected to the capacitors 73 but also in the topend of the contact plug 83 a electrically connected to the bit line 76and contact plug 75. Therefore the conductive film 66 of the contactplug 83 a is not oxidized during formation of the dielectric films 71 ofcapacitors 73. This reduces the contact resistance between the bit line76 or contact plug 75 and the source/drain regions 59.

The second preferred embodiment has shown a method for manufacturing asemiconductor device that has concave-type MIM capacitors as DRAM memorycell capacitors 73. However, as has been mentioned in the firstpreferred embodiment, the present invention can be applied also tomethods for manufacturing semiconductor devices in which capacitors 73are MIM capacitors with other structures. For example, the presentinvention can be applied also to methods for manufacturing semiconductordevices having supported cylinder-type MIM capacitors as shown in FIG.31, pillar-type MIM capacitors as shown in FIG. 32, and thick-filmstacked-type MIM capacitors as shown in FIG. 33.

When pillar-type MIM capacitors or thick-film stacked-type MIMcapacitors are adopted, the aspect ratios of contact plugs 25, 75 can besmaller. Therefore, as shown in FIGS. 34 and 35, the contact plugs 25and interconnections 26, or the contact plug 75 and bit line 76 may beintegrally formed using dual damascene process.

When thick-film stacked-type MIM capacitors are adopted, the interlayerinsulating film 18 in the insulating film 31 is removed during themanufacturing process. Therefore FIGS. 33 and 35 do not show it.

Third Preferred Embodiment

The second preferred embodiment provides the conductive barrier layers82 in the top ends of the contact plugs 83 a and 83 b in the memoryregion. However, during formation of the dielectric films 71 ofcapacitors 73, the contact plugs 33 in the logic region may also beoxidized, as well as those in the memory region.

Therefore a third preferred embodiment describes a manufacturing methodin which conductive barrier layers are formed also in the top ends ofthe contact plugs 33 in the logic region.

FIGS. 36 to 42 are cross-sectional views showing a sequence of processsteps of the semiconductor device manufacturing method of the thirdpreferred embodiment. First, the structure shown in FIG. 4 is obtainedaccording to the manufacturing process of the first preferredembodiment. Then, as shown in FIG. 36, without using resist, the entiresurface is etched to selectively remove the top ends of the conductivefilms 66 in the memory region and the top ends of the conductive films16 in the logic region. Thus, recesses 81 are formed in the insulatingfilm 14 in the memory region and recesses 41 are formed in theinsulating film 14 in the logic region. This etching adopts ananisotropic dry-etching process using SF₆ as the etching gas.

Next, a barrier layer material of, e.g. titanium nitride, tantalumnitride, or titanium silicide nitride, is formed all over the surface tofill the recesses 41 and 81, and the barrier layer material above therecesses 41 and 81 is removed, e.g. by CMP. Thus, as shown in FIG. 37,conductive barrier layers 82 filling the recesses 81 are formed in theinsulating film 14 in the memory region. Also, conductive barrier layers42 of titanium nitride, tantalum nitride, or titanium silicide nitridefilling the recesses 41 in the logic region are formed in the insulatingfilm 14.

These process steps form a contact plug 83 a and contact plugs 83 b inthe insulating film 14 in the memory region; the contact plug 83 a hasconductive barrier layer 82 in the top end and each contact plugs 83 b,too, has conductive barrier layer 82 in the top end. In the logicregion, contact plugs 33 having conductive barrier layers 42 in theirtop ends and conductive films 16 in the remaining portions are formed inthe insulating film 14. Like the conductive barrier layers 82, theconductive barrier layers 42 have lower conductivity than the conductivefilms 16 and 66.

Next, as shown in FIG. 38, stopper film 17 and interlayer insulatingfilm 18 are deposited in this order on the insulating film 14 andcontact plugs 33, 83 a and 83 b. Then, as shown in FIG. 39, as in thefirst preferred embodiment, openings 69, capacitors 73, and interlayerinsulating films 23 are sequentially formed. The capacitors 73 shown inFIG. 39 are concave-type MIM capacitors.

Next, as shown in FIG. 40, resist 38 having opening patterns 39 a and 39b is formed on the insulating film 31. The interlayer insulating films18 and 23 and stopper film 17 are etched and removed away using theresist 38 as a mask. This process forms contact holes 24 respectivelyreaching the conductive barrier layers 42 of the contact plugs 33 and acontact hole 74 reaching the conductive barrier layer 82 of the contactplug 83 a in the insulating film 31.

Next, after removal of the resist 38, as shown in FIG. 41, contact plugs25 filling the contact holes 24 and contact plug 75 filling the contacthole 74 are formed. Thus the conductive barrier layers 42 of the contactplugs 33 and the contact plugs 25 are in contact respectively with eachother and the conductive barrier layer 82 of the contact plug 83 a andthe contact plug 75 are in contact with each other.

Next, as shown in FIG. 42, interconnections 26 and bit line 76 areformed on the insulating film 31.

Thus a memory device is formed in the memory region and a logic deviceis formed in the logic region.

As described above, according to the semiconductor device manufacturingmethod of the third preferred embodiment, the oxidation-preventingconductive barrier layers 42 are formed in the top ends of the contactplugs 33 provided in the lower layer in the logic region, as well asthose in the top ends of the contact plugs 83 a and 83 b in the memoryregion. Therefore the conductive films 16 of the contact plugs 33 arenot oxidized during formation of the dielectric films 71 of capacitors73. This further lowers the contact resistance between the contact plugs25 provided in the upper layer and the source/drain regions 9 in thelogic region.

The third preferred embodiment has shown a method for manufacturing asemiconductor device that has concave-type MIM capacitors as DRAM memorycell capacitors 73. However, as has been mentioned in the first andsecond preferred embodiments, the present invention can be applied alsoto methods for manufacturing semiconductor devices in which capacitors73 are MIM capacitors of other structures. For example, the presentinvention can be applied also to methods for manufacturing semiconductordevices having supported cylinder-type MIM capacitors as shown in FIG.43, pillar-type MIM capacitors as shown in FIG. 44, and thick-filmstacked-type MIM capacitors as shown in FIG. 45.

When pillar-type MIM capacitors or thick-film stacked-type MIMcapacitors are adopted, the aspect ratios of the contact plugs 25, 75can be smaller. Therefore, as shown in FIGS. 46 and 47, the contactplugs 25 and interconnections 26, or the contact plug 75 and bit line 76may be integrally formed using dual damascene process.

When thick-film stacked-type MIM capacitors are adopted, the interlayerinsulating film 18 in the insulating film 31 is removed during themanufacturing process. Therefore FIGS. 45 and 47 do not show it.

Fourth Preferred Embodiment

In the semiconductor device manufactured by the method of the thirdpreferred embodiment, as shown in FIG. 42, the conductive barrier layers42 and 82, serving as oxidation preventing films, remain in the top endsof the contact plugs 33 and 83 a. However, the conductive barrier layers42 and 82 may be removed after the formation of capacitors 73 becausethey are not necessary any more. A fourth preferred embodiment describesa method in which the conductive barrier layers 42 and 82 are removedafter the formation of capacitors 73.

FIGS. 48 to 50 are cross-sectional views showing a sequence of processsteps for manufacturing a semiconductor device according to the fourthpreferred embodiment of the invention. First, the structure shown inFIG. 39 is obtained according to the process of the third preferredembodiment. Then, as shown in FIG. 48, resist 38 having opening patterns39 a and 39 b is formed on the insulating film 31. Then, using theresist 38 as a mask, the interlayer insulating films 18 and 23 areetched and removed away using the stopper film 17 as an etching stopper.This etching adopts an anisotropic dry-etching process using a mixed gasof C₄F₆, O₂ and Ar. Then, using a different etching gas, and using theresist 38 as a mask again, the exposed parts of the stopper film 17 areetched away. This etching adopts an anisotropic dry-etching processusing CHF₃ as the etching gas.

Thus, contact hole 74 reaching the contact plug 83 a and contact holes24 reaching the contact plugs 33 are formed through the insulating film31.

Next, using another etching gas, and using the resist 38 as a mask, theexposed conductive barrier layers 42 and 82 are etched and removed away.This etching adopts an anisotropic dry-etching process using a mixed gasof Cl₂ and CHF₃.

Thus, in the memory region, a recess 93 communicating with the contacthole 74 is formed in the insulating film 14, with the conductive film 66of the contact plug 83 a being exposed. Also, in the logic region,recesses 43 communicating with the contact holes 24 are formed in theinsulating film 14, with the conductive films 16 of the contact plugs 33being exposed.

Next, after removal of resist 38, a refractory metal film of, e.g.tungsten, is formed all over the surface to fill the recesses 43, 93 andcontact holes 24, 74. Then, the refractory metal film on the top surfaceof the insulating film 31 is removed, e.g. by CMP. Thus, as shown inFIG. 49, in the logic region, contact plugs 25, filling the contactholes 24 and recesses 43, are formed in the insulating films 14 and 31,and the conductive films 16 of the contact plugs 33 are in contactrespectively with the contact plugs 25. Also, in the memory region, acontact plug 75 filling the contact hole 74 and recess 93 is formed inthe insulating films 14 and 31, and the conductive film 66 of thecontact plug 83 a is in contact with the contact plug 75. Subsequently,as shown in FIG. 50, interconnections 26 and bit line 76 are formed onthe insulating film 31, thus completing a merged memory-logicsemiconductor device.

As described above, in the semiconductor device manufacturing method ofthe fourth preferred embodiment, the conductive barrier layer 82 formedin the top end of the contact plug 83 a in the memory region is removedafter the formation of capacitors 73. Therefore the contact plug 75 inthe upper layer is in contact with the conductive film 66 of the contactplug 83 a in the lower layer. The conductive film 66 has a higherconductivity than the conductive barrier layer 82. The contactresistance between the upper-layer contact plug 75 and the lower-layercontact plug 83 a is therefore lower than when the upper-layer contactplug 75 is in contact with the conductive barrier layer 82 of thelower-layer contact plug 83 a, as described in the method of the thirdpreferred embodiment. This further lowers the contact resistance betweenthe contact plug 75 or bit line 76 and the source/drain regions 59.

Furthermore, since the conductive barrier layers 42 formed in the topends of contact plugs 33 in the logic region are removed after formationof capacitors 73, the contact plugs 25 in the upper layer are in contactrespectively with the conductive films 16 of the contact plugs 33 in thelower layer. The conductive films 16 have a higher conductivity than theconductive barrier layers 42. The contact resistance between theupper-layer contact plugs 25 and the lower-layer contact plugs 33 istherefore lower than when the upper-layer contact plugs 25 are incontact with the conductive barrier layers 42 of the lower-layer contactplugs 33 as described in the method of the third preferred embodiment.This further lowers the contact resistance between the contact plugs 25and source/drain regions 9.

Moreover, in the fourth preferred embodiment, the conductive barrierlayers 42 and 82 are removed using the resist 38 that is used to formthe contact holes 24 and 74 in the insulating film 31, using a differentetching gas. The conductive barrier layers 42 and 82 can thus be removedby a smaller number of process steps.

Fifth Preferred Embodiment

FIG. 51 is a cross-sectional view showing the structure of asemiconductor device according to a fifth preferred embodiment of theinvention. The semiconductor device of the fifth preferred embodimenthas contact plugs 25 that are differently shaped from those in thestructure shown in FIG. 42. Therefore some contents already described inthe first to fourth preferred embodiments are not described again hereto show the semiconductor device of the fifth preferred embodiment.

As shown in FIG. 51, the semiconductor device of the fifth preferredembodiment has: semiconductor substrate 1; insulating film 14 providedon the semiconductor substrate 1; contact plugs 33, 83 a, 83 b formed inthe insulating film 14; capacitors 73 residing on the insulating film 14and being in contact with the contact plugs 83 b; insulating film 31lying on the insulating film 14 and covering capacitors 73; contactplugs 25, 75 formed in the insulating film 31; and interconnections 26and bit line 76 lying on the insulating film 31.

Element isolation insulating films 2 are formed in the upper surface ofthe semiconductor substrate 1. Also, well region 3 is formed in theupper surface of the semiconductor substrate 1 in the logic region andwell region 53 is formed in the upper surface of the semiconductorsubstrate 1 in the memory region.

A plurality of source/drain regions 9 are provided at a given distancein the upper surface of the well region 3, and a plurality ofsource/drain regions 59 are provided at given distances in the uppersurface of the well region 53.

Gate structure 11 is provided on the upper surface of the well region 3between adjacent source/drain regions 9, and gate structures 61 areprovided on the upper surface of the well region 53 between adjacentsource/drain regions 59.

Silicide films 12 are provided on the top surface of the gate electrode6 of the gate structure 11 and on the top surfaces of the gateelectrodes 56 of the gate structures 61. Silicide films 12 are formedalso on the source/drain regions 9 and 59.

The top surfaces of the contact plugs 33, 83 a, 83 b are exposed fromthe insulating film 14. Each contact plug 83 b is electrically connectedthrough silicide film 12 to one of adjacent source/drain regions 59, andthe contact plug 83 a is electrically connected through silicide film 12to the other of adjacent source/drain regions 59. Contact plugs 33 areelectrically connected through silicide films 12 to the source/drainregions 9.

In the memory region, the contact plug 75 is in contact with the topsurface of the conductive barrier layer 82 of the contact plug 83 a, andthe top surface of the contact plug 75 is exposed from the insulatingfilm 31. Bit line 76 is in contact with the contact plug 75.

In the logic region, the top surfaces of the contact plugs 25 areexposed from the insulating film 31 and are in contact with theinterconnections 26. Each contact plug 25 extends into the insulatingfilm 14 and is in contact with the conductive barrier layer 42 of thecontact plug 33 and also in contact with part of the side surface of thetop portion of the conductive film 16.

In this way, according to the semiconductor device of the fifthpreferred embodiment, even when the contact plugs 33 in the logic regionhave oxidation-preventing conductive barrier layers 42, the upper-layercontact plugs 25 are in contact not only with the conductive barrierlayers 42 of the lower-layer contact plugs 33 but also with theconductive films 16 having higher conductivity. Therefore, the contactresistance between the upper-layer contact plugs 25 in the logic regionand the source/drain regions 9 in the semiconductor substrate 1 is lowerthan when the upper-layer contact plugs 25 are electrically connectedwith the conductive films 16 through the conductive barrier layers 42 asshown in the semiconductor device of FIG. 42.

Furthermore, the conductive barrier layers 82 in the top ends of thecontact plugs 83 b that are in contact with capacitors 73 preventoxidation of the conductive films 66 of the contact plugs 83 b duringformation of the dielectric films 71 of capacitors 73. Thus, even whenoxidation process is performed for formation of the dielectric films 71of capacitors 73, it is possible to achieve both of a reduction incontact resistance in the memory device and a reduction in contactresistance in the logic device.

Next, a method for manufacturing the semiconductor device shown in FIG.51 is described referring to FIGS. 52 to 55. First, the structure shownin FIG. 39 is obtained according to the manufacturing process of thethird preferred embodiment. Next, as shown in FIG. 52, a resist 38 isformed on the insulating film 31.

Then, as shown in FIG. 53, opening patterns 39 a and 39 b are formedthrough the resist 38 in correspondence respectively with the positionsof the contact plugs 33 and 83 a. In this process, the opening patterns39 a above the contact plugs 33 are intentionally somewhat misalignedwith, or shifted from, the contact plugs 33. Therefore, as shown in FIG.53, the opening patterns 39 a extend not only right above the contactplugs 33 but also right above the insulating film 14.

The opening pattern 39 b above the contact plug 83 a is positioned justright above the contact plug 83 a, without being intentionallymisaligned with the contact plug 83 a. In the fifth preferredembodiment, the diameter of the opening patterns 39 a is set almost thesame as the diameter of the contact plugs 33 and the diameter of theopening pattern 39 b is set almost the same as the diameter of thecontact plug 83 a.

Next, as shown in FIG. 54, using as a mask the resist 38 having openingpatterns 39 a and 39 b, the interlayer insulating films 18 and 23 arepartially etched and removed away using the stopper film 17 as anetching stopper. This etching adopts an anisotropic dry-etching processusing a mixed gas of C₄F₆, O₂ and Ar.

Then, using the resist 38 as a mask again, the exposed parts of thestopper film 17 are etched away by anisotropic dry-etching using CHF₃ asthe etching gas, so as to form contact holes 24 passing through theinsulating film 31 to respectively reach the contact plugs 33 and acontact hole 74 reaching the contact plug 83 a. During this process, thestopper film 17 is over-etched for a given amount so that the contactholes 24 extend into the insulating film 14, whereby side surfaces ofthe conductive films 16 of the contact plugs 33 are exposed.

As shown above, since the opening patterns 39 a are misaligned with thecontact plugs 33, the opening patterns 39 a are located not only rightabove the contact plugs 33 but also right above the insulating film 14.Accordingly, in the logic region, the insulating film 14, too, is etchedby the over-etch of the stopper film 17. It is thus possible, byover-etching the stopper film 17 for a given amount, to expose not onlythe conductive barrier layers 42 of the contact plugs 33 but also partsof the side surfaces of top portions of the conductive films 16.

The opening pattern 39 b is positioned only right above the contact plug83 a, so that the insulating film 14 is not etched in the memory region.Also, the conductive barrier layer 82 of the contact plug 83 a is hardlyetched by the etching gas used to remove the stopper film 17, so thatthe conductive barrier layer 82 remains in the top end of the contactplug 83 a after the formation of the contact hole 74.

Next, as shown in FIG. 55, contact plugs 25 are formed to fill thecontact holes 24 and a contact plug 75 is formed to fill the contacthole 74. Thus, the contact plugs 25 are formed not only through theinsulating film 31 but also into the insulating film 14; they thus comein contact respectively with the conductive barrier layers 42 of thecontact plugs 33 and also respectively with parts of the side surfacesof the top portions of the conductive films 16. Subsequentlyinterconnections 26 and bit line 76 are formed on the insulating film 31to obtain the semiconductor device shown in FIG. 51.

As shown above, according to the semiconductor device manufacturingmethod of the fifth preferred embodiment, even when oxidation-preventingconductive barrier layers 42 are formed in the top ends of the contactplugs 33 in the logic region, the upper-layer contact plugs 25 are incontact not only with the conductive barrier layers 42 of thelower-layer contact plugs 33 but also with the conductive films 16having higher conductivity. Therefore the contact resistance between theupper-layer contact plugs 25 in the logic region and the source/drainregions 9 provided in the semiconductor substrate 1 is lower than whenthe upper-layer contact plugs 25 are electrically connected to theconductive films 16 through the conductive barrier layers 42 as shown inthe semiconductor device manufacturing method of the third preferredembodiment.

Furthermore, the conductive barrier layers 82 in the top ends of thecontact plugs 83 b prevent oxidation of the conductive films 66 of thecontact plugs 83 b during formation of the dielectric films 71 ofcapacitors 73. Therefore it is possible to achieve both of a reductionin contact resistance in the memory device and a reduction in contactresistance in the logic device.

In the fifth preferred embodiment, the upper-layer contact plug 75 inthe memory region is in contact only with the conductive barrier layer82 of the contact plug 83 a but is not in contact with the conductivefilm 66. However, as shown in the semiconductor device of FIG. 56, thecontact plug 75 may be extended into the insulating film 14 so that itcomes in contact also with a side surface of the conductive film 66 ofthe lower-layer contact plug 83 a.

Thus, even when the contact plug 83 a in the memory region hasoxidation-preventing conductive barrier layer 82, forming theupper-layer contact plug 75 in contact with the conductive film 66 ofthe lower-layer contact plug 83 a lowers the contact resistance betweenthe upper-layer contact plug 75 or bit line 76 and the source/drainregions 59 in the semiconductor substrate 1.

A method for manufacturing the semiconductor device shown in FIG. 56 isnow described referring to FIGS. 57 and 58.

First, the structure shown in FIG. 39 is obtained according to theprocess of the third preferred embodiment. Then, as shown in FIG. 57, aresist 38 is formed on the insulating film 31. Then opening patterns 39a and 39 b are formed through the resist 38 in correspondencerespectively with the positions of the contact plugs 33 and 83 a. Inthis process, like the opening patterns 39 a above the contact plugs 33,the opening pattern 39 b above the contact plug 83 a, too, isintentionally slightly misaligned with, or shifted from, the contactplug 83 a. Thus, the opening pattern 39 b is positioned not only rightabove the contact plug 83 a but also right above the insulating film 14.

Next, as shown in FIG. 58, using as a mask the resist 38 having openingpatterns 39 a and 39 b, the interlayer insulating films 18 and 23 arepartially etched and removed away using the stopper film 17 as anetching stopper.

Then, using the resist 38 as a mask again, the exposed parts of thestopper film 17 are etched away by anisotropic dry-etching using CHF₃ asthe etching gas, so as to form contact holes 24 and 74 through theinsulating film 31. During this process, the stopper film 17 isover-etched for a given amount so that the contact holes 24 and 74extend into the insulating film 14, whereby side surfaces of theconductive films 16 of the contact plugs 33 are exposed and a sidesurface of the conductive film 66 of the contact plug 83 a is exposed,too.

As shown above, since the alignment of the opening pattern 39 b with thecontact plug 83 a is shifted, the opening pattern 39 b is located notonly right above the contact plug 83 a but also right above theinsulating film 14. Accordingly, by the over-etch to the stopper film17, the insulating film 14 is etched not only in the logic region butalso in the memory region. It is thus possible to expose not only theconductive barrier layer 82 of the contact plug 83 a but also to exposepart of the side surface of the top portion of the conductive film 66,by over-etching the stopper film 17 for a given amount.

Next, contact plugs 25 are formed to fill the contact holes 24 and acontact plug 75 is formed to fill the contact hole 74. Thus, like thecontact plugs 25, the contact plug 75 is formed not only through theinsulating film 31 but also into the insulating film 14; it thus comesin contact with the conductive barrier layer 82 of the contact plug 83 aand also with part of the side surface of the top portion of theconductive film 66. Subsequently, interconnections 26 and bit line 76are formed on the insulating film 31 to obtain the semiconductor deviceshown in FIG. 56.

As shown above, even when oxidation-preventing conductive barrier layer82 is formed in the top end of the contact plug 83 a in the memoryregion, the upper-layer contact plug 75 is in contact not only with theconductive barrier layer 82 of the lower-layer contact plug 83 a butalso with the conductive film 66 having higher conductivity. Thereforethe contact resistance between the upper-layer contact plug 75 in thememory region and the source/drain regions 59 in the semiconductorsubstrate 1 is lowered.

While the fifth preferred embodiment has shown semiconductor deviceshaving concave-type MIM capacitors as DRAM memory cell capacitors 73 andmanufacturing methods thereof, the present invention can be applied alsoto semiconductor devices and manufacturing methods in which MIMcapacitors with other structures are used as capacitors 73. For example,the present invention can be applied also to semiconductor devices andmanufacturing methods using supported cylinder-type MIM capacitors asshown in FIG. 59, pillar-type MIM capacitors as shown in FIG. 60, andthick-film stacked-type MIM capacitors as shown in FIG. 61.

When pillar-type MIM capacitors or thick-film stacked-type MIMcapacitors are adopted, the aspect ratios of the contact plugs 25, 75can be smaller. Therefore, as shown in FIGS. 62 and 63, the contactplugs 25 and interconnections 26, or the contact plug 75 and bit line 76may be integrally formed using dual damascene process.

When thick-film stacked-type MIM capacitors are adopted, the interlayerinsulating film 18 in the insulating film 31 is removed during themanufacturing process. Therefore FIGS. 61 and 63 do not show it.

Sixth Preferred Embodiment

FIG. 64 is a cross-sectional view showing the structure of asemiconductor device according to a sixth preferred embodiment of theinvention. The semiconductor device of the sixth preferred embodimenthas contact plugs 25 that are shaped differently from those in thesemiconductor device of the fifth preferred embodiment.

As shown in FIG. 64, in the semiconductor device of the sixth preferredembodiment, the top surfaces of the contact plugs 25 are exposed fromthe insulating film 31 and are in contact with interconnections 26. Thediameter of the contact plugs 25 is larger than the diameter of thecontact plugs 33 and they extend into the insulating film 14. Thecontact plugs 25 are in contact respectively with the conductive barrierlayers 42 of the contact plugs 33 and also in contact respectively withthe entire peripheries of the side surfaces of top portions of theconductive films 16. In other respects the structure of thesemiconductor device is the same as that of the fifth preferredembodiment and is not described again here.

In this way, according to the semiconductor device of the sixthpreferred embodiment, even when the contact plugs 33 in the logic regionhave oxidation-preventing conductive barrier layers 42, the upper-layercontact plugs 25 are in contact not only with the conductive barrierlayers 42 of the lower-layer contact plugs 33 but also with the entireperipheries of the side surfaces of the top portions of the conductivefilms 16 having higher conductivity. Therefore, the contact resistancebetween the upper-layer contact plugs 25 in the logic region and thesource/drain regions 9 in the semiconductor substrate 1 is lower than inthe semiconductor device of the fifth preferred embodiment in whichcontact plugs 25 are in contact only with parts of the side surfaces ofthe top portions of the conductive films 16.

Next, a method for manufacturing the semiconductor device shown in FIG.64 is described referring to FIGS. 65 to 67. The same contents alreadydescribed about the semiconductor device manufacturing method of thefifth preferred embodiment are not described again here.

First, the structure shown in FIG. 39 is obtained according to themanufacturing method of the third preferred embodiment. Next, as shownin FIG. 65, a resist 38 is formed on the insulating film 31.

Then, opening patterns 39 a and 39 b are formed through the resist 38 incorrespondence respectively with the positions of the contact plugs 33and 83 a. In this process, the diameter of the opening patterns 39 aabove the contact plugs 33 is set larger than the diameter of thecontact plugs 33, without intentional misalignment with the contactplugs 33. Therefore, as shown in FIG. 65, the opening patterns 39 a arepositioned not only right above the contact plugs 33 but also rightabove parts of the insulating film 14 around the contact plugs 33.

Next, as shown in FIG. 66, using as a mask the resist 38 having openingpatterns 39 a and 39 b, the interlayer insulating films 18 and 23 arepartially etched and removed away using the stopper film 17 as anetching stopper.

Then, using the resist 38 as a mask again, the exposed parts of thestopper film 17 are etched away by anisotropic dry-etching using CHF₃ asthe etching gas, so as to form contact holes 24 passing through theinsulating film 31 to reach the contact plugs 33 and to form a contacthole 74 reaching the contact plug 83 a. During this process, the stopperfilm 17 is over-etched for a given amount so that the contact holes 24extend into the insulating film 14 to expose the entire peripheries ofthe side surfaces of top portions of the conductive films 16 of thecontact plugs 33.

As shown above, since the diameter of the opening patterns 39 a islarger than the diameter of the contact plugs 33, the opening patterns39 a are located not only right above the contact plugs 33 but alsoright above parts of the insulating film 14 around the contact plugs 33.Accordingly, by over-etching the stopper film 17 for a given amount, theinsulating film 14 is also etched, and it is possible to expose not onlythe conductive barrier layers 42 of the contact plugs 33 but also toexpose the entire peripheries of the top portions of the side surfacesof the conductive films 16.

Next, as shown in FIG. 67, contact plugs 25 are formed to fill thecontact holes 24 and a contact plug 75 is formed to fill the contacthole 74. Thus, the contact plugs 25 are formed not only through theinsulating film 31 but also into the insulating film 14; they thus comein contact respectively with the conductive barrier layers 42 of thecontact plugs 33 and also respectively with the entire peripheries ofthe side surfaces of top portions of the conductive films 16.Subsequently, interconnections 26 and bit line 76 are formed on theinsulating film 31 to obtain the semiconductor device shown in FIG. 64.

As shown above, according to the semiconductor device manufacturingmethod of the sixth preferred embodiment, even when oxidation-preventingconductive barrier layers 42 are formed in the top ends of the contactplugs 33 in the logic region, the upper-layer contact plugs 25 are incontact not only respectively with the conductive barrier layers 42 ofthe lower-layer contact plugs 33 but also respectively with the entireperipheries of the side surfaces of top portions of the conductive films16 having higher conductivity. Therefore the contact resistance betweenthe upper-layer contact plugs 25 in the logic region and thesource/drain regions 9 in the semiconductor substrate 1 is lower than inthe semiconductor device manufacturing method of the fifth preferredembodiment.

In the sixth preferred embodiment, as in the fifth preferred embodiment,the upper-layer contact plug 75 in the memory region is in contact onlywith the conductive barrier layer 82 of contact plug 83 a, but not incontact with the conductive film 66. However, as shown in thesemiconductor device of FIG. 68, the contact plug 75 may be extendedinto the insulating film 14 so that it comes in contact with the entireperiphery of the side surface of a top portion of the conductive film 66of the lower-layer contact plug 83 a.

Then, even when the contact plug 83 a in the memory region hasoxidation-preventing conductive barrier layer 82, forming theupper-layer contact plug 75 in the memory region in contact with theentire periphery of a side surface of the conductive film 66 in thelower-layer contact plug 83 a further lowers the contact resistancebetween the upper-layer contact plug 75 or bit line 76 and thesource/drain regions 59 in the semiconductor substrate 1.

A method for manufacturing the semiconductor device shown in FIG. 68 isnow described referring to FIGS. 69 and 70.

First, the structure shown in FIG. 39 is obtained according to theprocess of the third preferred embodiment. Then, as shown in FIG. 69, aresist 38 is formed on the insulating film 31. Then opening patterns 39a and 39 b are formed through the resist 38 in correspondence with thepositions of the contact plugs 33 and 83 a. In this process, like theopening patterns 39 a above the contact plugs 33, the diameter of theopening pattern 39 b above the contact plug 83 a, too, is set largerthan the diameter of the contact plug 83 a, without intentionalmisalignment with the contact plug 83 a. Therefore, the opening pattern39 b is positioned not only right above the contact plug 83 a but alsoright above part of the insulating film 14 around the contact plug 83 a.

Next, as shown in FIG. 70, using as a mask the resist 38 having openingpatterns 39 a and 39 b, the interlayer insulating films 18 and 23 arepartially etched and removed away using the stopper film 17 as anetching stopper.

Then, using the resist 38 as a mask again, the exposed parts of thestopper film 17 are etched away by anisotropic dry-etching using CHF₃ asthe etching gas, so as to form contact holes 24 and 74 through theinsulating film 31. During this process, the stopper film 17 isover-etched for a given amount so that the contact holes 24 and 74extend into the insulating film 14 to expose the entire peripheries ofthe side surfaces of top portions of the conductive films 16 of thecontact plugs 33 and also to expose the entire periphery of the sidesurface of the top portion of the conductive film 66 of the contact plug83 a.

As shown above, since the diameter of the opening pattern 39 b is largerthan the diameter of the contact plug 83 a, the opening pattern 39 b islocated not only right above the contact plug 83 a but also right abovepart of the insulating film 14 around it. Therefore, over-etching thestopper film 17 for a given amount exposes not only the conductivebarrier layer 82 of the contact plug 83 a but also the entire peripheryof the side surface of the top portion of the conductive film 66.

Next, contact plugs 25 are formed to fill the contact holes 24 and acontact plug 75 is formed to fill the contact hole 74. Thus, like thecontact plugs 25, the contact plug 75 is formed not only through theinsulating film 31 but also into the insulating film 14; it thus comesin contact with the conductive barrier layer 82 of the contact plug 83 aand also with the entire periphery of the side surface of the topportion of the conductive film 66. Subsequently interconnections 26 andbit line 76 are formed on the insulating film 31 to obtain thesemiconductor device shown in FIG. 68.

As shown above, even when oxidation-preventing conductive barrier layer82 is formed in the top end of the contact plug 83 a in the memoryregion, the upper-layer contact plug 75 is in contact not only with theconductive barrier layer 82 of the lower-layer contact plug 83 a butalso with the entire periphery of the side surface of the top portion ofthe conductive film 66 having higher conductivity. Therefore the contactresistance between the upper-layer contact plug 75 in the memory regionand the source/drain regions 59 in the semiconductor substrate 1 isfurther lowered.

While the sixth preferred embodiment has shown semiconductor deviceshaving concave-type MIM capacitors as DRAM memory cell capacitors 73 andmethods for manufacturing it, the present invention can be applied alsoto semiconductor devices and manufacturing methods in which MIMcapacitors with other structures are used as capacitors 73. For example,the present invention can be applied also to semiconductor devices andmanufacturing methods that use supported cylinder-type MIM capacitors asshown in FIG. 71, pillar-type MIM capacitors as shown in FIG. 72, andthick-film stacked-type MIM capacitors as shown in FIG. 73.

When pillar-type MIM capacitors or thick-film stacked-type MIMcapacitors are adopted, the aspect ratios of the contact plugs 25, 75can be smaller. Therefore, as shown in FIGS. 74 and 75, the contactplugs 25 and interconnections 26, or the contact plug 75 and bit line 76may be integrally formed using dual damascene process.

When thick-film stacked-type MIM capacitors are adopted, the interlayerinsulating film 18 in the insulating film 31 is removed during themanufacturing process. Therefore FIGS. 73 and 75 do not show it.

While the invention has been described in detail, the foregoingdescription is in all aspects illustrative and not restrictive. It isunderstood that numerous other modifications and variations can bedevised without departing from the scope of the invention.

1-20. (canceled)
 21. A semiconductor device comprising: a semiconductorsubstrate having a memory region where a memory device is formed and alogic region where a logic device is formed; a first insulating filmprovided on said semiconductor substrate; first and second contact plugsprovided in said first insulating film with their respective topsurfaces exposed from said first insulating film, and electricallyconnected to said semiconductor substrate in said memory region; a thirdcontact plug provided in said first insulating film with its top surfaceexposed from said first insulating film, and electrically connected tosaid semiconductor substrate in said logic region; an MIM capacitorhaving a lower electrode, an upper electrode, and a dielectric filminterposed therebetween, said lower electrode being in contact with thetop surface of said first contact plug; a second insulating filmprovided on said first insulating film and covering said MIM capacitor;a fourth contact plug provided in said second insulating film and beingin contact with said second contact plug; and a fifth contact plugprovided in said second insulating film and being in contact with saidthird contact plug; said first contact plug having a first conductivebarrier layer in its top portion and a first conductive film in aremaining portion; said third contact plug having a third conductivebarrier layer in its top portion and having, in a remaining portion, athird conductive film having a higher conductivity than said thirdconductive barrier layer; said fifth contact plug extending into saidfirst insulating film and being in contact with said third conductivebarrier layer and a side surface of said third conductive film.
 22. Thesemiconductor device according to claim 21, wherein said fourth andfifth contact plugs are in contact with the entire periphery of saidside surface of said second conductive film.
 23. The semiconductordevice according to claim 21, further comprising: first and secondsource/drain regions formed at a given distance from each other in anupper surface of said semiconductor substrate in said memory region; anda gate structure provided on the upper surface of said semiconductorsubstrate between said first and second source/drain regions, whereinsaid first insulating film is provided on said semiconductor substrateand covers said gate structure, said first and second contact plugs areelectrically connected respectively with said first and secondsource/drain regions, said fourth contact plug has its top surfaceexposed from said second insulating film and said semiconductor devicefurther comprises a bit line provided on said second insulating film andbeing in contact with said fourth contact plug.